Damon was born in Cambridge, Massachusetts, the son of Kent T. Damon, an investment banker and realtor, and Nancy Carlsson-Paige, an early-childhood education professor. His maternal grandfather, John Walter Paige, was an immigrant from Finland.[1] His brother Kyle is an accomplished artist and sculptor. He graduated from Cambridge Rindge and Latin in 1988, the only public high school in Cambridge, MA. Damon's first film job was one line in the romantic comedy Mystic Pizza (1988). He went on to attend Harvard University, but dropped out a few credits shy of graduating to pursue his acting career, a move that brought him to Los Angeles.

Damon appeared in small roles in a few movies before landing a big part in Geronimo: An American Legend with Gene Hackman and Jason Patric. He next appeared as a heroin-addicted soldier in 1996's Courage Under Fire. The war film was an opportunity for Damon to show his dedication by undergoing an extensive weight loss to help portray his character, as he was required to lose 40 pounds in 100 days (for only two days of shooting). After following a self-prescribed diet and fitness regimen to lose the weight, Damon was advised after the filming that he was fortunate his heart did not shrink. Damon was required to be on medication for several years to correct the stress inflicted on his adrenal gland, but maintains it was worthwhile to properly reflect his character's anguish and to show the industry how committed he was to the role.

Damon and actor Ben Affleck, close personal friends as well as co-stars in several films, developed a thriller about a young math genius, which they pitched around Hollywood. Receiving advice from writer/director/actor Rob Reiner and screenwriter William Goldman, the two changed the script around to focus on a young math genius trying to make his way in the world. This eventually became Good Will Hunting, which earned both Damon and Affleck Oscars for Best Original Screenplay. Damon was also nominated for an Academy Award for Best Actor for the same film (which netted an Oscar for Best Supporting Actor for co-star Robin Williams). Much of the credit for getting the film made goes to both executive producer Kevin Smith and Harvey Weinstein, Miramax Films chairman, to whom Smith gave the screenplay after the studio had originally passed on the script.

Damon also founded Project Greenlight with Affleck and Chris Moore to find and fund worthwhile film projects from novice filmmakers. The televised documentary about the making of the film projects has twice been nominated for an Emmy.

Damon has been known to stray from the mainstream in his choice of roles, such as his portrayal of murderer Tom Ripley in The Talented Mr. Ripley, a fallen angel who waxes pop culture as intellectual subject matter in Dogma, in which he costarred with Affleck (1999), and the low budget and experimental film Gerry.

Damon also played amnesiac assassin Jason Bourne in the successful action movies The Bourne Identity and The Bourne Supremacy, with another Bourne sequel, The Bourne Ultimatum, expected in 2007.

He will next be seen onscreen playing the Andy Lau character in Martin Scorsese's The Departed , a remake of the famous Hong Kong police thriller Infernal Affairs, and in Robert DeNiro's The Good Shepherd as a career man in the C.I.A.. He also has a supporting role in Kenneth Lonergan's film Margaret, due in late 2006, and an uncredited cameo in Francis Ford Coppola's Youth Without Youth, due in 2007.

It has recently been rumored that the new Star Trek director J.J. Abrams is trying to get Damon to play a young James Tiberius Kirk in the upcoming Star Trek prequel of Kirk and Spock in their Starfleet Academy days. Previously rumored for the part was Damon's long time friend Ben Affleck.

While filming Stuck on You in 2003, Damon met Argentine-born Luciana Boz�n Barroso at Crobar in Miami Beach, where she was working as a bartender. They married in a private civil ceremony on December 9, 2005 in New York City Hall. Damon became stepfather to Barroso's young daughter, Alexia, from a previous marriage. The couple's first child together, daughter Isabella, was born on June 11, 2006, in Miami.

Prior to meeting Barroso, Damon had dated actresses Claire Danes, Minnie Driver and Winona Ryder, as well as model Bridget Hall and Ben Affleck's former personal assistant, Odessa Whitmire. He has admitted he wrote the female lead character of Skylar in 1997's Good Will Hunting about his real-life former girlfriend, Skylar Satenstein, whom he dated while attending Harvard University. Satenstein later married Metallica drummer Lars Ulrich, although they are now divorced.

To promote the film Rounders with Edward Norton, Damon and Norton were entered by Miramax into the 1998 World Series of Poker main event $10,000 buy-in No Limit Texas Hold'em. Damon was eliminated on the first day by poker legend Doyle Brunson.